Let's start at the very beginning with the basic definitions that you'll come across when looking at digital cameras. A lot of the terminology will also be the same as 35mm film photography — so if you're familiar with analogue photography, never fear.

Digital cameras can be classified as either a compact (left) or SLR (right).
(Credit: CBSi)

Though it sounds very basic, understanding what a camera is will help you understand how it works. The principle has remained the same since the beginning of photography — a camera captures light in order to form an image.

Put simply, light from the subject enters the camera's lens, which helps focus and direct the rays onto either the film plane or image sensor.

There are two main types of digital cameras: compacts and SLRs. We will be covering SLR cameras in more detail in our next instalment of the Learning Centre.

What is a megapixel?

Resolution

Traditionally we would talk about resolution as just a count of the pixels.

pixels wide x pixels high= resolution

As we will see later on, other elements of a digital camera (such as the lens and image sensor size) play a huge part in determining the true resolution that an image sensor can deliver.

A pixel is the smallest component that makes up a digital image. The megapixel value you'll find written on your camera simply means how many pixels (or photo sensors) are on your image sensor. The mega denotes one million.

A camera's megapixel count relates to the resolution of the image it is able to produce. Unless you are aiming to make very large prints of your digital images, more often than not a 10- or 12-megapixel sensor will produce a large enough file for you to work with for 10x15cm prints all the way to A3 size.

The table below shows the equivalent megapixel to resolution conversions. Note these are calculated based on a standard 4:3 aspect ratio — we'll explain this later when we talk about image sensors.